In an aircraft gas turbine (jet) engine, air is drawn into the front of the engine, compressed by a shaft-mounted compressor, and mixed with fuel. The mixture is burned, and the hot exhaust gases are passed through a turbine mounted on the same shaft. The flow of combustion gas turns the turbine by impingement against an airfoil section of the turbine blades and vanes, which turns the shaft and provides power to the compressor. The hot exhaust gases flow from the back of the engine, driving it and the aircraft forwardly.
In some gas turbine engines, there is an exhaust nozzle flap structure at the back of the engine. The exhaust nozzle flap structure is formed of a series of individual exhaust nozzle flap segments arranged in a generally cylindrical fashion around the periphery of the engine at its exhaust end. The exhaust nozzle flap segments may be pivoted inwardly or outwardly, so as to change the size of the outlet passage through which the hot exhaust gases flow. This change in geometry alters the performance of the engine in a controllable manner. Each exhaust nozzle flap segment includes inner flaps which contact the hot combustion gas flow to shape it, and an outer flap which ensures aerodynamic efficiency.
Each of the exhaust nozzle flap segments is supported on a pivot structure at its forwardmost end. The inner and outer flaps are connected to each other and to the remainder of the engine structure in the form of a geometric linkage. The linkage includes an exhaust nozzle compression link. When the exhaust nozzle flap segment is moved by an actuator, the exhaust nozzle compression link aids in maintaining the correct geometrical relation of the inner flaps and the outer flap. The exhaust nozzle compression link is subjected to large compressive loads by the aerodynamic forces exerted by the combination of the hot combustion gas on the inner flaps and the external air flow on the outer flap.
The exhaust nozzle compression link is a vital component in the actuation of the flap structure. In conventional construction, the exhaust nozzle compression link is a rectangular-section hollow strut with a fitting at each end. The exhaust nozzle compression link is made of a nickel-base superalloy in order to withstand heating to about 800.degree. F. resulting from the hot exhaust gases, while providing the necessary compressive strength to support the flap structure and the aerodynamic loading.
There is always a desire to reduce the weight of aircraft gas turbine engines, while retaining acceptable performance. Weight reductions in the area of the exhaust nozzle are highly beneficial to aircraft performance and maneuverability, because of the distance of the exhaust nozzle from the center of gravity of the aircraft. The need to reduce weight to achieve these benefits extends to individual components, such as the exhaust nozzle compression link. The present invention fulfills the need for reduced weight and acceptable performance, and further provides related advantages.